Lower, Mark A (1860) Patronymica Britannica: a dictionary of the family names of the United Kingdom. London: J.R. Smith. Public Domain.
NEILSON
As described in historical dictionaries
Patronymica Britannica (1860)
NEILSON.* " Three brothers of the sirname of Oneal, came from Ireland to Scotland, in the reign of Robert the Bruce, where they got lands for their valour, and their issue changed their name a little from Oneal to Neilsou ; for Oneal and M'Neil are the same with Ncilson." jSTisbet. The first occurrence of the name noted by this author is in 1439, in Galloway.
Surname type: From given name or forename
Origin: Celtic
Region of origin: British Isles
Country of origin: Scotland
Religion of origin: Christian
Language of origin: Gaelic